How do I create a hinged door?
The easiest way (without rigging or armatures) is to displace the origin of the object on the edge you want to use as hinge.

Go to Edit mode and select the edge. Then press ShiftS to use the snap menu. Snap the cursor to selected.

In Object mode use Object->transform->Origin to 3D cursor. The origin of the object will be now on the edge of the door.

Rotate the object (in this case on the local Z axis).



For more complex objects or movements beyond local axis it's better to use bones and a rig.